1. Field of the Invention
The subject invention generally pertains to sectional doors and more specifically to a latch assembly for such a door.
2. Description of Related Art
A sectional door typically includes a series of panels whose adjacent horizontal edges are connected by hinges. As the door opens or closes, the door panels travel along two lateral tracks that, for some door styles, curve between horizontal and vertical. To close the door, the tracks guide the panels to a vertical position across the doorway. When the door opens, the hinges allow the panels to curve around onto horizontal sections of the tracks, where the door panels store horizontally overhead. For other door styles, the sectional door maintains a generally vertical, planar configuration and is stored more directly above the doorway. Such doors, regardless of their configuration, are often open and closed manually. To ease the operation of the door, a torsion spring is often used to counteract the weight of the door panels. Sectional doors are commonly used as residential garage doors; however, they are also often used in warehouses and other industrial buildings.
When used in high-traffic industrial applications, overhead-storing doors are very susceptible to being struck by large trucks, trailers, forklifts and other vehicles passing through the doorway. Collisions are often caused by a door's torsion spring becoming weak with age or not being properly preloaded, which can allow a door to droop or not stay in its fully open position. Consequently, an upper edge of a vehicle may catch the lower edge of the door, and thus break or damage the door.
Holding a sectional door fully open without relying solely on the door's torsion spring can be accomplished by a safety catch disclosed in U.S. Pat. No. 3,426,829. Such a catch includes a spring that urges the catch to an extended position. In this position, the catch is able to engage the underside of a roller or its shaft to prevent the door from accidentally falling down to its closed position. To release the door, a solenoid pulls on the catch. This rotates the catch out from underneath the roller, which allows the door to close. Such a device, however, has a few drawbacks.
For example, as the door opens, several rollers or their shafts repeatedly snap the catch between its extended position and a release position, as the rollers or their shafts travel past the catch. The wasted snapping movement of the catch can create noise, as well as create wear on various parts of the door and wear on the catch itself. Moreover, to release the door out from underneath the catch, the catch rotates in such a way as to first raise the door panels slightly before allowing them to descend. Thus, the weight of the door could add significantly to the force needed in moving the catch to its release position.